Apparatus for the predetermined addition of secondary air for the optimum combustion of exhaust gases of internal combustion engines

ABSTRACT

Apparatus for the predetermined addition of secondary air used in effecting optimum combustion of internal combustion engine exhaust gases, including a control arrangement including one or more measuring parameters sensing engine operating or exhaust gas contents and, in response to the sensed conditions, regulating the addition of secondary air in order to obtain optimum exhaust gas combustion.

CROSS-RELATED APPLICATION

This application is a division of Ser. No. 356,193 filed May 1, 1973 andissued Jan. 13, 1976 as U.S. Pat. No. 3931,710.

FIELD OF THE INVENTION

The present invention relates to apparatus for the measurement ofsupplementary or secondary air utilized for obtaining the optimumcombustion or after-burning of the exhaust gases of internal combustionengines, and in which the added quantity of the secondary air isdetermined by means of a control installation. It has been ascertainedas being essential that deleterious materials, which are present in theexhaust gases of the internal combustion engines, such as carbonmonoxide (CO), hydrocarbons (C_(x) H_(Y)) and nitric oxide (NO_(x)), beconverted through suitable means into harmless chemical compounds. Inorder to accomplish this effect, thermally and catalytically operatingreactors or after-burners are generally utilized.

DISCUSSION OF THE PRIOR ART

When an internal combustion engine is driven under variable operativeconditions, there occur constant changes in the composition of theexhaust gases. The foregoing changes disturb the after-burning sequence,inasmuch as at any particular time there is experienced an excess, andat another time, a shortage of oxygen available for use in theafter-burning process. In order to compensate for these shortcomings, itis presently known that the internal combustion engines may be operatedwith a deficiency or insufficiency of air (λ is less than 1), and tointroduce the combustion air required for the after-burning by means ofa motor-driven air pump. An arrangement of that type is described andillustrated in German laid-open specification No. 2,035,591.

A drawback of the prior art installations consists of in that theadditive quantities of secondary air cannot be controlled in a preciseand sufficiently rapid manner. Consequently, the after-burner cannot beoptimally operated, and the deleterious materials in the exhaust gasescannot be adequately converted into harmless components.

SUMMARY OF THE INVENTION

The present invention, accordingly, has, as an object, the optimalconversaion of the deleterious materials contained in the exhaust gasesof an internal combustion engine into harmless materials within theextent of the most advantageous engine air-fuel mixture relationship,and for which purpose there is provided a precision control arrangementfor the addition of secondary air.

The problems encountered in the prior art are herein inventively solvedin that the control arrangement for the addition of secondary air iscoordinated from at least three external control or guide conditionswhich are in a non-linear interdependent relationship with each other.Advantageously, an additional control guide condition provides furtherexternal guidance into the control installation, and acts independentlyof the other control guide conditions.

Advantageously, as the control guide conditions, there may be utilizedthe pressure on the suction side (suction conduit presure), the pressureon the exhaust side (exhaust gas back-pressure), the engine speed orR.P.M., the oxygen or the carbon monoxide content of the exhaust gases,either concurrently or selectively.

In a further embodiment of the invention one or more non-linearinterdependent control guide conditions may be influenced by theindependent or separate control guide condition.

As a sensor for the measurement of the extent of oxygen or carbonmonoxide contained in the exhaust gases there may be employed a suitablemeasuring receiver having a platinum-coated wall or partition which isformed of zirconium oxide and located whereby the wall on one surfacethereof is in communication with the exhaust gases being measured and onits other surface with the atmosphere.

In order to obtain an improved degree of control and concurrentlyprovide for the relief of the air inlet arrangement, the controlinstallation for the introduction of measured quantities of thesecondary air is additionally provided with an arrangement for thewithdrawal and return of a portion of the air which is conveyed into thecontrol installation. This allows for the addition of the secondary airquantities and the withdrawal of the returning quantities of air throughthe use of two conical metering plug valves mounted one above the otheron a common actuating rod, and which are so positioned relative to eachother, whereby upon an increase in the quantity of secondary air, thequantity of returning withdrawal air is reduced and reversed.

The actuating rod for the conical metering plug valves advantageously isfixedly connected with two superimposed spaced membranes havingdifferent active or operative surfaces, and in which a control pressurechamber positioned inntermediate the membranes preferably is subjectedto the exhaust gas back-pressure, and a second control pressure chamberpositioned above the upper membrane is subjected to the suction tubepressure. In the foregoing construction, the control presure chamberwhich is located above the upper membrane is provided with an inletaperture having a non-return valve positioned therein, so that inflowinto the control pressure chamber is essentially unrestricted, and withthe non-return valve being bridged by a narrow bypass aperture so thatany outflow from the control pressure chamber is only permitted throughthe bypass aperture. Consequently, upon a sudden withdrawal of gases,this will prevent the sudden cut-off of the inflow of secondary air.

In order to prevent the forming of an undue high pressure at the inletside to the inflowing air, the arrangement for the withdrawal and returnof a portion of the air flowing into the control installation, in afurther embodiment of the invention is provided with a closure memberwhich allows for the return flow as soon as the pressure of theinflowing air reaches a predetermined value. This closure member may beintegrally formed with the conical metering plug valve employed for thereturn flow.

In order to obtain an additional influence over the control guideconditions per se, in another embodiment of the invention there may beprovided suitable actuating members in the signal conduits providing oneor more of the non-linear interdependent control guide conditions. Toobtain this effect, there may be located a signal converter ortransformer intermediate the sensors used for the measurement of theoxygen content or of the carbon monoxide content of the exhaust gasesand the actuating members of one or more of the signal conduits for thenon-linearly interdependent control guide conditions.

In a further embodiment there may be provided, in lieu of or in additionto, a control element at the output of the control installation for theaddition of the secondary air, which is actuated in response to thesignals emanating from a signal converter, the latter of which receivesand converts the signals from the sensors measuring the oxygen or carbonmonoxide contents of the exhaust gases.

So long as the secondary air for the internal combustion engine must beconveyed into the suction conduit, it is preferable that downstream ofthe control element positioned at the outlet of the control installationand used for the addition of secondary air, there is included a controlvalve through which the secondary air flows for maintaining constant thepressure at the valve inlet. When employing pneumatic signal conduits,preferably used are calibrated throttling valves which afford animproved degree of integration of the control impulses.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now had to preferred embodiments of the present invention,taken in conunction with the accompanying drawings, in which:

FIG. 1 illustrates an internal combustion engine air intake and exhaustsystem showing a control installation according to the presentinvention;

FIG. 2 is a second embodiment of a control installation;

FIG. 3 is a third embodiment of a control installation;

FIG. 4 illustrates an internal combustion engine air intake and exhaustsystem showing a fourth embodiment of a control installation;

FIG. 5 illustrates the system of FIG. 4 with a fifth embodiment of acontrol installation;

FIG. 6 illustrates the system of FIG. 4 with a sixth embodiment of acontrol installation; and

FIG. 7 illustrates a modified system with a seventh embodiment of acontrol installation.

DETAILED DESCRIPTION

In accordance with the embodiment of FIG. 1, an internal combustionengine 11 includes on its suction side a suction conduit 12 which has acarburetor 13 attached to one end thereof. The inlet of air is effectedthrough an air filter 14. The combustion fuel inlet and air-fuel mixtureforming components of the carburetor are not illustrated.

At its exhaust side, the internal combustion engine 11 includes anexhaust collecting conduit 15 which leads toward an after-burner 16. Anair pump 17 is connected with a filter 19 through a suction conduit 18,and through which filter secondary air is aspirated from the atmosphere.From the air pump 17 a conduit 20 communicates with a controlinstallation 21. An air return conduit 22 leads from the controlinstallation 21 back into suction conduit 18.

The control installation 21 includes a multiple-component housing 23which is divided by means of membranes 24 and 25 into control pressurechambers 26 and 27, and through partitions 28 and 29 into pressurechambers 30, 31 and 32. The conduit 20 communicates with the pressurechamber 31, and the air return conduit 22 with the pressure chamber 30.

The membrane 25 has a larger effective or operative surface thanmembrane 24. Both membranes are fixedly connected to a control rod 33,which has positioned thereon and fastened thereto in superimposedrelationship conical measuring valves 34 and 35. The conical valves arecooperatively positioned in, respectively, passages 40 and 41 located inthe respective partitions 28 and 29.

Utilized as the non-linear interdependent control parameters are thesuction tube pressure, the exhaust gas back-pressure, and the enginespeed or R.P.M. The suction tube pressure is communicated into thecontrol installation 21 through conduit 36, and the exhaust gasback-pressure through conduit 37. The engine R.P.M. or rotational speedis similarly transmitted into the control installation 21 through adrive 38 directly to the air pump 17, and indirectly air supplyquantity, which is dependent upon engine R.P.M., of conduit 20. Thesecondary air is introduced through conduit 39 into the exhaust gascollecting conduit 15.

In the engine stationary operating mode, both conical measuring orcalibrating valves are moved into their lowermost position due to theforce of a compression spring 42 acting on membrane 24, so as to closeaperture 40 and completely open aperture 41.

During engine operation the air pump 17 pumps, in response to apredetermined engine R.P.M., correspondingly larger or smaller airquantities. At a high suction tube pressure compression spring 42 isunloaded, in view of which the conical valves are downwardly displaced.Consequently, the return flow of secondary air from pressure chamber 31into the pressure chamber 30 and from there into the air return conduit22 is either reduced or completely stopped, whereas the aperture 41 ismore or less opened so as to allow for the passage therethrough ofsecondary air from pressure chamber 31 into the pressure chamber 32 andfrom the latter through conduit 39 into the exhaust gas collectingconduit 15. The lower the suction tube pressure, the higher are conicalvalves 34 and 35 raised, so as to permit that much more air to bereturned, while restricting the delivery of secondary air.

The exhaust gas back-pressure which is present in conduit 39 iscommunicated through conduit 37 as the control parameter for the controlpressure chamber 27. In view of the area or surface differential ofmembranes 24 and 25, an increasing exhaust gas back-pressure creates anincreased opening, whereas a reducing exhaust gas back-pressure createdthe continued closing of aperture 41.

FIG. 2 illustrates another specific embodiment of a control installation21. In the following details this embodiment advantageouslydistinguishes over the control installation according to FIG. 1:

In the upper portion of the multiple component housing 23 there islocated an adjusting screw 43 which provides for the adjustment of thepre-stressing or loading of compression spring 42, and a secondadjusting screw 44 for adjustment of the minimum cross-sectional openingof aperture 41. The control pressure chamber 27 communicates through abore 45 and a channel 46 with pressure chamber 32, the latter of whichcommunicates through conduit 39 with the exhaust gas collecting conduit15. This eliminates the requirement for a particular conduit (forexample, conduit 37 in FIG. 1).

The control installation 21 of the embodiment according to FIG. 3 of thedrawings evidences further advantages as compared to the controlinstallation illustrated in FIG. 2. Thus, the control pressure chamber26 located above membrane 24 includes an inlet aperture 47 in whichthere is positioned a non-return valve 48 formed of a spring-loadedball, and in view of the action of which, the air inlet flow fromconduit 36 into control pressure chamber 26 is essentially unrestricted.By means of a bypass aperture 49 the non-return valve 48 is bridged in amanner so as to allow air outflow from the control pressure chamber 26only through the bypass aperture 49. The conical valve 34 in thisembodiment is slidably mounted on the control rod 33 and is biased by acompression spring 50. Consequently, the conical valve 34 concurrentlyforms a closure member which permits air return flow as soon as thepressure of the inflowing air reaches a predetermined value. This isfurther attained independently of the operative position of the otherconical valve 35. This arrangement advantageously and in a single mannerprotects the apparatus against the unallowable excess pressures.

In FIG. 4 there is illustrated another embodiment of the invention,which in the following essentials distinguishes over the embodiment ofFIG. 1:

In a signal conduit 51; 51a for the control installation 21 whichemploys the encountered exhaust gas back-pressure as the control guidecondition, there is utilized a control element 52 which is constitutedof an electro-magnetically actuated three-way valve. The withdrawal ofthe exhaust gas back-pressure, in this instance, is not obtained fromconduit 39 but, in a manner similar to FIGS. 2 and 3, from the pressurechamber 32. Upstream of the after-burner 16, a sensor 53 is located inthe exhaust gas collecting conduit 15 so as to facilitate themeasurement of the oxygen content in the exhaust gases. The sensorconsists of a measured value receiver which includes a platinum-coatedwall formed of zirconium oxide. The measured value receiver ispositioned so that the wall communicates with one surface thereof withthe exhaust gases being measured, and its other surface with theatmosphere.

The sensor 53 conveys a voltage signal, dependent upon the continuouslymeasured oxygen content of the exhaust gases, through an electricalconduit 54 into a signal converter or transformer 55. The signalconverter 55, which is basically a conventional threshold circuitnormally used with an exhaust gas sensor, by means of a conduit 56 and asuitable accumulator battery (not shown), has an operative directcurrent supplied thereto. The signal converter 55 emanates anintermittent output signal which is conveyed through a conduit 57 to thecontrol element 52. The membrane chamber 27 is subjected to an exhaustgas back pressure which leads to an increase in the secondary airaddition, until the sensor 53 again reports the flow of exhaust gascomposition toward a leaner direction. The control sequence againrepeats continuously in the aforementioned manner, so as to be able toprovide intermittent control of the electromagnet valve 52.

A single conduit 58 branches from conduit 36 and similarly leads througha non-return valve 59, a reserve container or vacuum storage accumulator60 and a vacuum signal conduit 61, to control element 52. The vacuum inthis storage accumulator 60 is generated through the conduits 58 and 36.As soon as the vacuum or reduced pressure in the suction tube 12 ishigher than the vacuum in the storage volume 60, the return valve 59 isopened and the receptacle 60 is evacuated. In all cases, in which thevacuum in receptacle 60 is higher than the reduced pressure in thesuction tube 12, the valve remains closed. The reduced pressure in thestorage 16 is required in order to provide for the availability ofvarious control pressures upon the switching over of the electromagneticthree-way valve 52. The control element 52 is in a position to, inaccordance with the received impulse signals, connect, with variableinterruption intervals, the signal conduit 51a with either the signalconduit 51 or 61. In dependence upon the interruption intervals, apredetermined pressure is generated in the control pressure chamber 27,so as to effect a precise regulation on the considerably differentlysized operative surfaces of the membranes 24 and 25.

In FIG. 5 a further embodiment of the invention is disclosed, whichvaries in the following particulars from the embodiment of FIG. 4:

The control element 52, in this instance, consists of anelectro-magnetically actuated through-flow valve. In a signal conduit 61there is positioned a second control element 62, which consists of asimilar electro-magnetically actuated through-flow valve. A conduit 57leads from the signal converter 55 to the control element 52, andanother conduit 63 leads to control element 62. In this embodiment, thecontrol of each of the control elements 62 and 52 may be effectedindependently of each other. This particular utilization provides for a"dead" or neutral range of the control between two signal impulse peakvalues, which allows for the switching frequency to be lowered, and areduction in the volume of the reserve container 60.

A further embodiment of the invention is illustrated in FIG. 6, andwhich varies in the following essentials from the embodiment of FIG. 1:

At the output of the control installation 21 for the addition of thesecondary air there is provided a control element 64 which is actuatedthrough the intermediary of conduit 57 by the output signals of signalconverter 55, the latter of which receives signals from sensor 53through conduit 54. In this embodiment the sensor 53 has, as describedin greater detail in FIG. 4, a platinum-coated wall formed of zirconiumoxide.

Through a conduit 56, the signal converter 55 is provided with anoperative direct current voltage from an accumulator battery (notshown). The advantage of this arrangement lies in that the unavoidabletime delays in commencing with air additions are still further reduced.

The inventive embodiment according to FIG. 7 shows, in contrast to allof the other embodiments, an addition of secondary air at the suctionside of the internal combustion engine. A further distinction lies inthat, in the conduit 39, 39a through which the secondary air is conveyedinto the suction conduit 12, there is positioned a secondary airthrough-flow control valve 65 which maintains the valve inlet pressureat a constant value. The control valve 65 consists of a housing 66 whichis divided by a membrane 67 into a control pressure chamber 68 and apressure chamber 69. Aln aperture 70 provides communication between thecontrol pressure chamber 68 and atmosphere. The membrane 67 which issubjected to a biasing force by a compression spring 71, duringinaction, locates a closure element 72 which is connected thereto into aclosed position. Upon the pressure in conduit 39 reaching apredetermined value, the valve outlet is opened by the closure element72 in opposition to the biasing force exerted by the spring-loadedmembrane 67.

The construction and switching action of the control element 64, thesignal converter 55, and of the sensor 53 corresponds to that describedin the embodiment of FIG. 6.

The quantity of the air conveyed from the air pump 17 in response to therotational speed of the engine, is conveyed through conduit 20 into thecontroll installation 21, whose function has been described inconnection with the embodiment of FIG. 1. The occasional disturbingoscillations which occur in the suction tube pressure are maintainedremote from the pressure chamber 32 of control installation 21 throughthe intermediary of the control valve 65. As distinguished from all ofthe other embodiments, the exhaust gas back-pressure is not conveyedthrough conduit 37, but the controlled pressure in the conduit 39 isconveyed as the control guide condition into the control pressurechamber 27 of the control installation 21.

The advantage of this arrangement consists in that the operative enginecombustion is effectively controlled by the addition of air and improvedthereby, and in which above all an even more increased constant controltime is obtained in comparison with the other embodiments of theinvention.

In addition to the above-enumerated advantages of the present inventionit is also emphasized that in view of the inventive fine precisioncontrol over the addition of secondary air, the conversion of thedeleterious materials which are contained in the exhaust gases of theinternal combustion engine are adapted to be converted into harmlesscomponents for the purposes of universal protection, to the optimumextent.

While there has been shown what is considered to be the preferredembodiment of the invention, it will be obvious that modifications maybe made which come within the scope of the disclosure of thespecification.

What is claimed is:
 1. Apparatus for the proportionate addition ofsecondary air to the inlet of an internal combustion engine foreffecting optimum combustion and after-burning of the exhaust gases fromthe internal combustion engine, said apparatus comprising anengine-driven air pump; control means for introducing predeterminedquantities of secondary air to the engine; means including a sensorlocated externally of said control means and responsive to at least oneof a plurality of engine operating conditions for regulating saidcontrol means; said control means including means for the withdrawal ofa portion of the secondary air conveyed through said control means andconducting said withdrawn secondary air to the suction side of said airpump, said air pump returning said secondary air from the pressure sideof said air pump to said control means; means for determining the rateof feed of the secondary air and the quantity of the air portionwithdrawn from said control means to said air pump, and means includingtwo spaced conical valve means controlling flow passages through saidcontrol means, said valve means being mounted on a common actuatingcontrol rod and being positioned so that, during an increase of the fedquantity of secondary air, the quantity of the withdrawn air portion isreduced, said actuating control rod for said conical valve means beingrigidly connected to two spaced upper and lower membranes having unequaloperative surfaces, said membranes defining therebetween a first controlpressure chamber, and a second control pressure chamber located abovethe upper membrane communicating with the suction inlet of said engineand secondary air control valve means coupled to said control means forreceiving pumped secondary air therefrom for supplying the secondary airto said engine inlet while maintaining constant pressure in said firstcontrol pressure chamber.
 2. Apparatus as claimed in claim 1 whereinsaid secondary air control valve means comprises an inlet chamber, anoutlet connected to said engine inlet, and a valve between said inletchamber and said outlet for maintaining constant pressure in said inletchamber, said first control pressure chamber being connected to saidinlet chamber to be at the same pressure therewith.
 3. Apparatus asclaimed in claim 2 wherein said means for regulating said control meanscomprises a control element controlling flow of pumped secondary airfrom said control means to said inlet chamber.
 4. Apparatus as claimedin claim 3 wherein said secondary air control valve means furthercomprises a membrane connected to said valve and forming a controlchamber subject to atmospheric pressure, and a pressure chamber incommunication with said inlet chamber, said pressure chamber having anoutlet constituting said outlet of the secondary air control valvemeans.
 5. Apparatus as claimed in claim 4 wherein said secondary aircontrol valve means further comprises a spring acting on said membranein opposition to the pressure in said pressure chamber.
 6. Apparatus asclaimed in claim 1 wherein said sensor determines the content of oxygenor carbon monoxide in the exhaust gases, said sensor including ameasured value receiver having a platinum-coated wall formed essentiallyof zirconium oxide, said wall having one surface in contact with theexhaust gases being measure and the opposite surface exposed toatmosphere.